1. Field of the Invention
This invention relates generally to elastomeric compositions and more specifically, to elastomeric compositions containing oriented glass microfibers and products made therefrom.
2. Description of the Related Art
Efforts continue in the tire industry to improve tire performance, especially in such areas as rolling resistance, durability and the ability of a tire to operate in a run-flat mode over an extended distance. Materials that are used in the tire as well as the tire construction are both important factors in achieving such improvements in tire performance. The materials undergoing research in the tire industry include rubber compositions having glass fibers incorporated into the blend.
The addition of fibers into a rubber composition is well known. For example, in European Patent Application EP 0 719 820, published Jul. 3, 1996, a rubber composition was disclosed as being suitable for use in the tread of tires. The disclosed rubber composition reportedly provided excellent rolling characteristics, abrasion resistance, and improved dimensional stability and further did not undergo excessive shrinkage when extruded into rubber sheets for treads. The rubber composition included silica as a reinforcing material to provide the improved rolling characteristics and dimensional stability. Organic fibers, e.g., nylon, aramid, polyester, rayon or cotton, were added to the rubber composition to limit the shrinkage of the resulting extruded rubber sheets made from the disclosed composition.
In U.S. Patent Application No. 2004/0035515, published Feb. 26, 2004, a studless tire was disclosed having a tread with fibers oriented in the tread-depth direction. These fibers, which could be either organic or inorganic fibers, had a Mohs hardness of 3 to 7 because fibers with a Mohs hardness of less than 3 are softer than ice so that the road scratching effect is insufficient and fibers with a Mohs hardness of more than 7 becomes harder than asphalt causing the road to shave. Examples of such materials were disclosed having glass fibers with an average fiber diameter of 33 μm and of 200 μm.
In U.S. Pat. No. 4,048,137, issued Sep. 13, 1977, an elastomeric material was disclosed that was reinforced with short small diameter insulating glass fibers. The glass fibers were disclosed as being treated with a silane coupling agent and further having lengths of between 3 to 50 mm and diameters of between 0.5 and 3.8 μm, preferably between 2.5 and 3.8 μm. It was disclosed that such glass fibers provide excellent reinforcement to elastomers.
In U.S. Pat. No. 6,209,604, issued Apr. 3, 2001, a pneumatic tire for passenger vehicles was disclosed having at least one sheet of a rubber-filament fiber composite in the sidewall. The fibers useful for the invention were disclosed as being both inorganic and organic fibers having diameters of between 0.0001 and 0.1 mm and having a length greater than at least 8 mm. The elastomer was disclosed as being applied to the non-woven fiber fabric having a thickness of between 0.05 mm and 2.0 mm.
In U.S. Pat. No. 6,631,748, issued Oct. 14, 2003, a pneumatic passenger tire suitable for use under run-flat conditions is disclosed having a sidewall insert. The sidewall insert is disclosed as having short fibers within the insert to provide additional rigidity to the sidewall. Suitable fibers are disclosed as being organic fibers such as rayon, nylon, polyester or aramid. It is further disclosed that the fibers may be positioned radially or at a bias but specifically not placed in a circumferential orientation.
As with many properties associated with tires, the change of one material or construction of a tire to improve one physical characteristic of the tire often results in the decrease of other physical characteristics of the tire. What are needed are materials that improve at least one tire characteristic while still providing a favorable mix of other physical characteristics.